400-007 · Question #226
An engineer must design a network for a company that uses OSPF LFA to reduce loops. Which type of loop would be reduced by using this design?
The correct answer is B. micro loops. OSPF LFA (Loop-Free Alternates) is specifically designed to prevent micro loops that can form during the brief convergence period after a topology change.
Question
An engineer must design a network for a company that uses OSPF LFA to reduce loops. Which type of loop would be reduced by using this design?
Options
- ADTP
- Bmicro loops
- CSTP
- DREP
How the community answered
(40 responses)- A3% (1)
- B95% (38)
- C3% (1)
Why each option
OSPF LFA (Loop-Free Alternates) is specifically designed to prevent micro loops that can form during the brief convergence period after a topology change.
DTP (Dynamic Trunking Protocol) is a Cisco Layer 2 protocol for negotiating trunk links between switches and is completely unrelated to OSPF or IP routing loops.
Micro loops occur in IP networks during convergence when different routers update their routing tables at different times after a link failure, causing packets to temporarily loop between routers. OSPF LFA precomputes backup next-hops that are mathematically guaranteed to be loop-free, allowing near-instant failover without waiting for full SPF reconvergence and eliminating the micro loop window.
STP (Spanning Tree Protocol) prevents Layer 2 broadcast loops in Ethernet networks and operates independently of OSPF or any Layer 3 routing protocol.
REP (Resilient Ethernet Protocol) is a Cisco proprietary Layer 2 ring topology protocol and has no relationship to OSPF LFA or IP-layer micro loops.
Concept tested: OSPF LFA loop-free alternate micro loop prevention
Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/xe-16/iro-xe-16-book/iro-loop-free-alternate.html
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